Embedded microfluidic distribution apparatus for passively cooling optoelectronic devices

Abstract

A device and method are provided for more efficient thermal management of optoelectronic devices. A microfluidic distribution apparatus embedded with the optoelectronic device uses a working fluid in phase change to passively remove heat from an optoelectronic device. The working fluid undergoes phase change through various conversions between a liquid state and a two-phase liquid-vapor state to facilitate evaporation and condensation processes as the working fluid is distributed through micro-structures in the embedded microfluidic distribution apparatus. Passive two-phase cooling provides high thermal performance due to the use of the latent heat of a fluid in phase change, as well as the presence of favorable two-phase flow regimes at micro-scale dimensions.

What is claimed is: 
     
       1. An apparatus for cooling an optoelectronic device, comprising:
 a microfluidic distribution apparatus positioned in an embedded arrangement with the optoelectronic device, the microfluidic distribution apparatus comprises: 
 a plurality of micro-structures forming a closed loop fluid distribution circuit; 
 an evaporator section having one or more of the micro-structures defined therein; 
 a condenser section having one or more of the micro-structures defined therein; and 
 an adiabatic section having one or more feeder micro-structures and one or more return micro-structures defined therein, the adiabatic section being in fluid communication with the evaporator section and the condenser section; 
 wherein the closed loop fluid distribution circuit comprises the one or more micro-structures in the evaporator section, the one or more feeder micro-structures and the one or more return micro-structures in the adiabatic section, and the one or more micro-structures in the condenser section; and 
 an evaporator inlet header section positioned between and in fluid communication with the one or more return micro-structures in the adiabatic section and the one or more micro-structures in the evaporator section, the evaporator inlet header section including a plurality of flow-directing structures; 
 wherein the microfluidic distribution apparatus is configured to distribute a working fluid capable of phase change to passively remove heat from the optoelectronic device by: 
 distributing the working fluid in the liquid state through the one or more microstructures in the evaporator section, wherein the working fluid converts to a two-phase liquid-vapor state via an evaporation process to remove heat generated by the optoelectronic device; 
 further distributing the working fluid in the two-phase liquid-vapor state through the one or more feeder micro-structures in the adiabatic section to the one or more microstructures in the condenser section where heat is passively dissipated to air in natural convection via a condensation process, wherein the working fluid converts from the two-phase liquid-vapor state back to the liquid state; 
 recirculating the working fluid converted back to the liquid state via the one or more return micro-structures in the adiabatic section back to the evaporator section; and 
 the plurality flow-directing structurers configured to facilitate a substantially uniform flow of the working fluid in the liquid state from the one or more return micro-structures in the adiabatic section into the one or more micro-structures of the evaporator section and to control backflow of the working fluid from the evaporator section to the one or more return micro-structures in the adiabatic section. 
 
     
     
       2. The apparatus according to  claim 1 , wherein the microfluidic distribution apparatus further comprises:
 a condenser distributor section positioned between and in fluid communication with the one or more feeder micro-structures in the adiabatic section and the one or more micro-structures in the condenser section, the condenser distributor section comprising: 
 a plurality of flow-directing structures having variable spacing therebetween such that a respective spacing between adjacent flow-directing structures from the plurality of flow-directing structures increases in the direction of the working fluid flowing from the one or more return micro-structures to facilitate a substantially uniform flow of the working fluid in the two-phase liquid-vapor state from the one or more feeder micro-structures into the one or more micro-structures of the condenser section. 
 
     
     
       3. The apparatus according to  claim 1 , wherein the plurality of flow-directing structures comprises:
 variable cross-sectional areas such that cross-sectional area of the plurality of flow-directing structures decreases in the direction of the working fluid flowing from the one or more return micro-structures. 
 
     
     
       4. The apparatus according to  claim 1 , wherein the plurality of flow-directing structures comprises:
 a plurality of apertures in fluid communication with the one or more micro-structures in the evaporator section, wherein respective diameters of the plurality of apertures increase in size in the direction of the working fluid flowing from the one or more return micro-structures in the adiabatic section. 
 
     
     
       5. The apparatus according to  claim 1 , wherein the microfluidic distribution apparatus and optoelectronic device are arranged in a vertical orientation, the evaporator section being positioned below the condenser section such that:
 distribution of the working fluid in the two-phase liquid-vapor state from the evaporator section toward the condenser section is facilitated by a buoyancy force; and 
 distribution of the working fluid in the liquid state returned from the condenser section toward the evaporator section is facilitated by a gravity force. 
 
     
     
       6. The apparatus according to  claim 5 , wherein the one or more micro-structures in the evaporator section comprise artificial nucleation sites to facilitate distribution of the working fluid in the two-phase liquid-vapor state from the evaporator section toward the condenser section. 
     
     
       7. The apparatus according to  claim 6 , wherein the artificial nucleation sites comprise any of:
 at least one perturbation in one or more surfaces of the one or more micro-structures in the evaporator section; and 
 at least one micro-structure positioned within the one or more micro-structures in the evaporator section. 
 
     
     
       8. The apparatus according to  claim 6 , wherein the artificial nucleation sites facilitate distribution of the working fluid in the two-phase liquid-vapor state from the evaporator section toward the condenser section by two-phase flow instabilities. 
     
     
       9. The apparatus according to  claim 1 , wherein the microfluidic distribution apparatus is positioned in the embedded arrangement with the optoelectronic device such that one or more heat-generating components on the optoelectronic device are substantially aligned with the evaporator section to facilitate heat transfer from the one or more heat-generating components into the evaporator section. 
     
     
       10. The apparatus according to  claim 9 , wherein the one or more heat-generating components are mounted on a substrate of the optoelectronic device, wherein the substrate includes a first buffer region and a second buffer region, the first buffer region being positioned proximate to a flow input side of the evaporator section for controlling backflow of the working fluid from the evaporator section, the second buffer region being positioned for controlling pre-boiling of the working fluid along surfaces joining the evaporator section and the one or more return micro-structures of the adiabatic section. 
     
     
       11. The apparatus according to  claim 1 , wherein the optoelectronic device is a comb laser source assembly comprising a plurality of reflective semiconductor optical amplifiers (RSOAs), and wherein the microfluidic distribution apparatus is positioned in the embedded arrangement with the optoelectronic device such that the RSOAs are substantially aligned with the evaporator section to facilitate heat transfer from the RSOAs into the evaporator section. 
     
     
       12. The apparatus according to  claim 11 , wherein the optoelectronic device further comprises an optical multiplexer/demultiplexer with an athermal structure operable for regulating temperature of the optoelectronic device for wavelength stabilization, the optical multiplexer/demultiplexer selected from the group of an athermal arrayed waveguide grating (AWG), an athermal echelle grating, a plurality of athermal ring resonators, and a plurality of athermal Mach-Zehnder interferometers. 
     
     
       13. The apparatus according to  claim 1 , wherein the evaporator section, the adiabatic section, and the condenser section are disposed between a first plate and a second plate to form the closed loop fluid distribution circuit. 
     
     
       14. The apparatus according to  claim 13 , wherein the embedded arrangement comprises the first plate or the second plate being in thermal and mechanical contact with a surface of the optoelectronic device. 
     
     
       15. The apparatus according to  claim 13 , wherein the first plate and the second plate are structures including material selected from the group of aluminum nitride (AlN), silicon, aluminum, and copper. 
     
     
       16. The apparatus according to  claim 13 , wherein the microfluidic distribution apparatus further comprises a sealable port for charging the working fluid. 
     
     
       17. A system for cooling an optoelectronic device, comprising:
 a microfluidic distribution apparatus positioned in an embedded arrangement with the optoelectronic device, the microfluidic distribution apparatus a first cooling loop and a second cooling loop, each of the first and second cooling loops comprising: 
 an evaporator section having a first plurality of micro-structures defined therein; 
 an adiabatic section having a plurality of feeder micro-structures and a plurality of return micro-structures defined therein; and 
 a condenser section having a second plurality of micro-structures defined therein, 
 the first plurality of micro-structures, the second plurality of micro-structures, the plurality of feeder micro-structures and the plurality of return micro-structures together forming a closed loop fluid distribution circuit; 
 an evaporator inlet header section positioned between and in fluid communication with the one or more return micro-structures in the adiabatic section and the one or more micro-structures in the evaporator section, the evaporator inlet header section including a plurality of flow-directing structures; 
 the microfluidic distribution apparatus configured to distribute a working fluid capable of phase change to passively remove heat from the optoelectronic device by: 
 distributing the working fluid in a liquid state through the first plurality of micro-structures in the evaporator section, wherein the working fluid converts to a two-phase liquid-vapor state and removes heat generated by the optoelectronic device via an evaporation process; and 
 distributing the working fluid in the two-phase liquid-vapor state through the plurality of feeder micro-structures in the adiabatic section to the second plurality of micro-structures in the condenser section where heat is passively dissipated to air in natural convection via a condensation process, wherein the working fluid converts from the two-phase liquid-vapor state back to the liquid state for recirculation via the plurality of return micro-structures in the adiabatic section back to the evaporator section; 
 the plurality of flow directing structures configured to facilitate a substantially uniform flow of the working fluid in the liquid state from the one or more return micro-structures in the adiabatic section into the one or more micro-structures of the evaporator section and to control backflow of the working fluid from the evaporator section to the one or more return micro-structures in the adiabatic section, and 
 wherein the first cooling loop and the second cooling loop are adjacently joined in a side-by-side configuration separated by a wall structure, such that the evaporator section and the plurality of feeder micro-structures of the adiabatic section in the first cooling loop are adjacent to the evaporator section and the plurality of feeder micro-structures of the adiabatic section in the second cooling loop. 
 
     
     
       18. The system according to  claim 17 , wherein the first cooling loop and the second cooling loop are configured such that a direction of flow of the working fluid in the first cooling loop is counter to a direction of flow of the working fluid in the second cooling loop.